We desire to continue our studies of the synthesis and conformational analysis of hypothalamic hormone releasing and inhibiting factors and to extend these studies to other biologically active peptides such as the opiate peptides from the brain. We will extend our investigations to include the synthesis of specifically labeled 15N-containing analogs of the luteinizing hormone releasing factor. The conformations of these peptides will be studied using 15N-nuclear magnetic resonance spectroscopy. We also plan to utilize a general approach we have developed to synthesize retroanalogs of the luteinizing hormone releasing factor, somatostatin and the enkephalins. Conformational analysis of these analogs, coupled with measurements of biological activity will provide valuable information concerning the interaction of the peptide backbone with the receptor. Finally we plan to use some analogs of the thyrotropin releasing factor and the luteinizing hormone releasing factor which we have already prepared to initiate a feasibility study concerned with both the affinity labeling and also the affinity purification of receptors for these hormones.